As is known, actinic radiations, particularly those comprises in the ultraviolet zone, adversely affect the appearance and the properties of the organic polymers. For example the polyester, usually colorless, yellows when exposed to sunlight; the oxidation rate of the polyolefins in air is greatly increased by ultraviolet light; polystyrene discolors and breaks, thus correspondingly losing its desirable properties, when exposed to actinic light, etc.
It has been proposed to stabilize the polymeric materials against degradation caused by ultraviolet light by employing various types of agents opposing such effects.
The sterically hindered amines (HALS) and in particular the derivatives of 2,2,6,6-tetra-alkyl-piperidine belong to such class of stabilizers.
In particular, U.S. Pat. No. 4,104,248 describes polymeric compounds of 4-amino-2,2,6,6-tetra-alkyl-piperidine to be utilized as stabilizers for polymeric substances against the degrading action of ultraviolet radiations and of oxygen.